By failing to deliver a performant and secure version of Flash (under any architecture, but especially mobile), Adobe ensured Flash would be not be viable for the web as it evolved.
Security was indeed an issue, but I feel flash’s performance reputation was largely undeserved. Yes, it was cpu-hungry, too intense to run on the mobile hardware of the day, but that’s because it did things html5 couldn’t. You could do smooth animations and complex games in flash easily that were hard to impossible to do with regular web tech (pre-webgl). When flash died, web animation and web gaming mostly died along with it. Some of that is the engine itself, and some is the flash authoring tools, which don’t have an open web equivalent. Maybe that sort of power never belonged in a browser, but I still feel like we lost something that didn’t fully get replaced.
I still largely blame Adobe here -- they were the ones who should have been responsible for fixing Flash's performance. The complaints about it being a CPU hog weren't limited to mobile; even in the early 2000s, Mac users, at least, generally hated being forced to deal with Flash-based UIs. Adobe never seemed real concerned with optimization, I suspect precisely because of the advantages you listed, e.g., things that were hard-to-impossible to do without Flash.
At this point, at least, I'm pretty sure WebGL can do most or all of what you could do in Flash. It's possible that the tools have never caught up, but it also seems possible to me that the space that used to be occupied by Flash games has largely been filled, ironically, by mobile gaming.
They where poor stewards of the platform, to be sure. The security situation was very bad, and they did little to discourage people from using Flash for all of the wrong reasons. But you could just as easily turn around and blame Apple for the depressing state of mobile gaming.
Apple didn’t kill Flash. Adobe did.
By failing to deliver a performant and secure version of Flash (under any architecture, but especially mobile), Adobe ensured Flash would be not be viable for the web as it evolved.